A Professor of Geophysics Emeritus and Associate Director of the Geophysical Institute, Professor Nielsen received his M.Sc. in 1965 from the Royal Technical University of Denmark. Professor Nielsen has a research background primarily in auroral and magnetospheric physics. At the institute, he has worked on optical auroral research and ionospheric and magnetospheric active experiments, notably the barium shaped-charge program. During the last 10 years he has investigated sprites, mesospheric discharges generated by tropospheric lightning, using high-speed optical methods.